Swimming refers to any combination of bodily movements employed by animals as a means of propelling themselves through water. Humans can learn to swim, although water is not their natural habitat. Fish, marine mammals, and other aquatic creatures swim by instinct as their primary means of locomotion.
Swimming is an Olympic sport. American Michael Phelps is probably considered to be the best swimmer to have ever lived, having won 18 gold medals. Some also cite this record to claim that Phelps is the greatest ever Olympian in any sport, but they ignore the fact that swimming has a disproportionate number of gold medals available, awarded for seemingly endless permutations of strokes, distances and relay races that make multiple medals an inevitability for the top competitors. Some Olympians with a strong claim to be greater than Phelps are Carl Lewis, Steve Redgrave, Chris Hoy, Ben Ainslie, Bradley Wiggins and Daley Thompson.
Many forms of competitive swimming, including medleys, the relay, the backstroke and synchronized swimming are joke sports.